An airless fluid dispensing system has been used in various applications for dispensing or applying fluids to an application site, which contains agents including medical products such as a nasal formulation, quasi-medical products such as a hair growth tonic, and cosmetic products such as a perfume.
Several airless fluid dispensing systems have so far been proposed, for example, Patent Document 1 discloses an airless pump container which includes a container body for holding fluid and an airless pump. The airless pump is adapted to pressurize fluid within a suction chamber upon downward depression of a nozzle, and release it into the atmosphere to spray the fluid from the nozzle, and also adapted to suck the fluid from the container body into the suction chamber upon upward return of the nozzle (see FIG. 2 thereof). The container body is provided with a bottom flap which is designed to slidably move along the side wall thereof upon receiving the atmospheric pressure, and in particular, moves upwardly with negative pressure in the container body as the fluid is sucked from the container body into the suction chamber. Thus, according to the airless pump container of Patent Document 1, even after the fluid within the container chamber is dispensed or sprayed, air is prevented from being introduced into the container body. Also, the invention of Patent Document 1 addresses to improve air-tightness (hermetic feature) between the bottom flap and the inner wall of the container body without increasing a sliding friction, by providing lower and upper inclined arms of resilient material with the bottom flap at the peripheral thereof contacting with the inner wall of the container body (see FIG. 3(A) thereof).
Another Patent Document 2 discloses a pump-type container with a content discharging mechanism which has a structure similar to that of Patent Document 1. The pump-type container has drawbacks, i.e., that some unused fluid is remained in an annular space between the container body and the bottom flap even after completion of the user's usage, and that an air bubble is trapped also in the annular space between the container body and the bottom flap when filled in with the fluid by a manufacturer. If the air bubble is trapped in the container body or the annular space, the user has to perform some pumping actions that is not required for actual dispense of the fluid to evacuate the air bubble from the container body and the suction chamber. Otherwise, a dosage of fluid may contain various volume, which is disadvantage especially when required to dispense a constant volume of the fluid such as medical products. However, repeating several pumping actions typically wastes the fluid for actual dosages. Therefore, the invention of Patent Document 2 suggests a substitution ceiling member having a flat bottom surface provided in the annular space of the container body, to eliminate unused fluid remained in an annular space between the container body and the bottom flap after completion of the usage, and the air bubble trapped when filled in with the fluid (see FIG. 1 thereof).    Patent Document 1: JPA 2003-212262    Patent Document 2: JPA 2006-044710